Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220601070707.3946847-1-saravanak@google.com>
 <20220601070707.3946847-8-saravanak@google.com> <20220622074756.GA1647@pengutronix.de>
 <CACRpkdYe=u9Ozj_dtLVr6GSau8yS5H7LnBNNrQHki1CJ1zST0A@mail.gmail.com> <CAGETcx_qm7DWbNVTLfF9jTgGA8uH8oAQzbPcMDh4L6+5mdRFog@mail.gmail.com>
In-Reply-To: <CAGETcx_qm7DWbNVTLfF9jTgGA8uH8oAQzbPcMDh4L6+5mdRFog@mail.gmail.com>
From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Tue, 28 Jun 2022 15:09:53 +0200
Message-ID: <CACRpkdYkbVWayPEukyKcSQuzMuV=BmhBwBA6GuoNvb3HLWLNUQ@mail.gmail.com>
Subject: Re: [PATCH v2 7/9] driver core: Set fw_devlink.strict=1 by default
To:     Saravana Kannan <saravanak@google.com>
Cc:     Sascha Hauer <sha@pengutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Kevin Hilman <khilman@kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>, kernel-team@android.com,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        iommu@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-gpio@vger.kernel.org, kernel@pengutronix.de
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Jun 22, 2022 at 9:40 PM Saravana Kannan <saravanak@google.com> wrote:

> Actually, why isn't earlyconsole being used? That doesn't get blocked
> on anything and the main point of that is to have console working from
> really early on.

For Arm (arch/arm) there is a special low-level debug option call low-level
debug, which you find in e.g:
arch/arm/Kconfig.debug
arch/arm/kernel/debug.S

This debug facility can print to the UART fifo before even MMU is up, pretty
much from the first instruction the kernel executes.

The versatility of LL-debug means that developers do not use earlyconsole
much on Arm.

I don't know about arm64 though.

Yours,
Linus Walleij